Embryonic Development Week 1-3

Embryonic Development

Week 1: Fertilization and Cleavage

• Fertilization: fusion of sperm and egg to form a zygote
• Cleavage: series of rapid cell divisions without significant growth
• Morula: stage at which cells begin to compact and form a solid ball
• Blastula: stage at which a fluid-filled cavity (blastocoel) forms

Week 2-3: Gastrulation

• Gastrulation: process of forming three primary germ layers
  • Ectoderm: outer layer, gives rise to skin, nervous system, and sensory organs
  • Mesoderm: middle layer, gives rise to muscles, bones, and connective tissue
  • Endoderm: inner layer, gives rise to lining of digestive system and respiratory system
• Gastrula: stage at which germ layers are established

Week 4-8: Organogenesis

• Organogenesis: process of forming organs from germ layers
• Neurulation: formation of neural tube, which gives rise to central nervous system
• Somitogenesis: formation of somites, which give rise to muscles, bones, and connective tissue
• Morphogenesis: shaping of tissues and organs

Embryonic Period (Week 3-8)

• Critical period of development, during which major organs and body systems form
• High susceptibility to teratogens, which can cause birth defects

Fetal Period (Week 9-Birth)

• Growth and maturation of organs and body systems
• Development of sensory organs and neural connections

Embryonic Stem Cells

• Totipotent: able to give rise to all cells in the body
• Pluripotent: able to give rise to all cells in the body, except for extra-embryonic tissues
• Multipotent: able to give rise to multiple cell types within a specific lineage
• Adult stem cells: multipotent cells found in adult tissues, able to differentiate into specific cell types

Embryonic Development

Week 1: Fertilization and Cleavage

• Fusion of sperm and egg forms a zygote through fertilization
• Series of rapid cell divisions without significant growth occurs during cleavage
• Morula stage: cells compact and form a solid ball
• Blastula stage: fluid-filled cavity (blastocoel) forms

Week 2-3: Gastrulation

• Gastrulation forms three primary germ layers: ectoderm, mesoderm, and endoderm
• Ectoderm gives rise to skin, nervous system, and sensory organs
• Mesoderm gives rise to muscles, bones, and connective tissue
• Endoderm gives rise to lining of digestive system and respiratory system
• Gastrula stage: germ layers are established

Week 4-8: Organogenesis

• Organogenesis forms organs from germ layers
• Neurulation forms neural tube, which gives rise to central nervous system
• Somitogenesis forms somites, which give rise to muscles, bones, and connective tissue
• Morphogenesis shapes tissues and organs

Embryonic Period (Week 3-8)

• Critical period of development, during which major organs and body systems form
• High susceptibility to teratogens, which can cause birth defects

Fetal Period (Week 9-Birth)

• Growth and maturation of organs and body systems
• Development of sensory organs and neural connections

Embryonic Stem Cells

• Totipotent stem cells can give rise to all cells in the body
• Pluripotent stem cells can give rise to all cells in the body, except for extra-embryonic tissues
• Multipotent stem cells can give rise to multiple cell types within a specific lineage
• Adult stem cells are multipotent cells found in adult tissues, able to differentiate into specific cell types

Learn about the early stages of embryonic development, including fertilization, cleavage, morula, blastula, and gastrulation. Understand the formation of primary germ layers and their significance.